/Engine/Source/Runtime/Engine/Classes/Materials/Material.h
LikeIsPropertyActive(), but should be used in context of editor. For example, there is an optimization that transforms masked materials into opaque materials in certain situations. If this optimization is active, the opacity mask input will no longer be active normally (since blend mode will be reported as opaque), but we still want to be able to connect this input from within the material editor.
bool IsPropertyActiveInEditor ( EMaterialProperty InProperty ) const